The present invention relates to a trigger assembly for an electric power tool.
The operation of electric hand drills is often controlled by means of a pull trigger, which is used to switch on and off the motor as well as to adjust the motor speed/torque. A typical trigger incorporates an electrical switch for main switching and an electronic control circuit for speed control. Sparks and debris produced by the switch may foul the control circuit.
The invention seeks to mitigate or at least alleviate such a problem by providing an improved trigger assembly.
According to the invention, there is provided a trigger assembly for an electric power tool including an electric motor, comprising a base for fixing within the tool and a trigger supported by the base for inward and outward movement. The base has a housing having first and second compartments separated by a partition that includes an aperture. A main switch is provided in the first compartment, having first and second contacts co-operable to switch the motor on and off. A slider is provided in the first compartment and is movable by or with the trigger for moving the first and second contacts into contact with one another or apart, the slider including a sliding contact. The base includes an electronic control circuit mounted on a circuit board located in the second compartment for controlling the operation of the motor. The circuit board includes at least one conductive track for contact by the sliding contact through the aperture. A shield extends around the aperture and is in abutment with the circuit board for blocking debris resulting from switching action of the main switch against reaching the circuit board beyond the track.
Preferably, the shield is provided at the periphery of the aperture.
More preferably, the shield is an integral rim portion of the aperture.
It is preferred that the shield protrudes from the aperture into abutment with the circuit board.
It is preferred that the partition is an integral part of the housing.
In a preferred embodiment, the main switch and the circuit board are provided on opposite sides of the slider, and the slider includes a baffle for blocking, at least partially, rapid dispersion of sparks and debris resulting from switching action of the main switch direct across the slider.
More preferably, the baffle extends over substantially the entire dimension of the slider or the first compartment.
More preferably, the baffle comprises a rib or flange.
More preferably, the baffle is an integral part of the slider.
The invention also provides an electric power tool including an electric motor and the aforesaid trigger assembly.
As an example, the electric power tool is an electric hand drill.